Hello, David!
Thanks for the nice explanation. However, I have question about the plasma potential.
If I’m not mistaken the plasma potential in gas discharge plasma is usually positive, because the plasma is positive respect to the wall. While the floating potential is negative due to the high mobility of electrons. So, you indicate that plasma potential is negative. Is it related to specific characteristics of your plasma source? Also, the positively biased part of you IV curve is very short and do you have any problem by collecting the electronica current data after increasing the applied voltage?

Thank you!